Category Archives: SQL

Improve SQL performance lead us to optimize AX performance, this post is one of posts to achieve that

1- Configuring max degree of parallelism

The max degree of parallelism option is a setting that affects the entire instance of SQL Server. Microsoft Dynamics AX workloads generally perform better when intra-query parallelism is disabled. However, the upgrade process benefits from parallelism, as do activities that are used exclusively for batch jobs or maintenance. Use the following settings when the system performs maintenance activities or an upgrade:

· Before an upgrade to a new release of Microsoft Dynamics AX, or before a large number of maintenance or batch activities, set max degree of parallelism to the smallest of the following values:

· 8

· The number of physical processor cores

· The number of physical processor cores per non-uniform memory access (NUMA) node

· When the Microsoft Dynamics AX database is used in a production environment, set max degree of parallelism to 1.

Use the following statements to set the value of max degree of parallelism.

Examine the output from the second sp_configure ‘max degree of parallelism’ statement, and confirm that the value has been changed. In the following query, the first sp_configure ‘max degree of parallelism’ statement sets the value of max degree of parallelism to 1. The second sp_configure ‘max degree of parallelism’ statement returns a value of 1.

SQL Server dynamically acquires and frees memory as required. Typically, an administrator does not have to specify how much memory is allocated to SQL Server. However, the max server memory option can be useful in some environments. Make sure that sufficient memory is available for the operation of Windows Server. For more information, see Configure SQL Server and storage settings, later in this topic.

If you find that the dynamic allocation of memory adversely affects the operation of Windows Server, adjust the value of max server memory based on the available random access memory (RAM). For more information, see Effects of min and max server memory.

3- Monitoring available memory

Make sure that sufficient memory is available for the operation of Windows Server. For example, make sure that you run a dedicated instance of SQL Server on a server that has at least 4 gigabytes (GB) of memory. If the available memory for the server drops below 500 megabytes (MB) for extended periods, the performance of the server may degrade.

Use the Memory: Available Mbytes performance counter for the Windows Server operating system to determine whether the available memory drops below 500 MB for extended periods. If the available memory drops below 500 MB frequently or for extended periods, we recommend that you reduce the max server memory setting for SQL Server or increase the physical memory of the server.

Detailed guidance about memory management is beyond the scope of this topic. For more information about how to monitor memory and troubleshoot performance issues, see the Windows Server and SQL Server documentation.

4- Allocating storage for tempdb

We recommend that you determine the total size of the data files and transaction log files that are required for the tempdb database, and that you set a specific value. Do not use automatic growth, or autogrow, setting for space management. Instead, use autogrow as a safety mechanism, so that tempdb can grow if tempdb files use the space that was originally allocated to them. Follow this process to determine the number and placement of data files.

· Determine the number of processors that are available to SQL Server. Unless you are using an affinity mask, this number is same as the total number of processors that you see on the Performance tab of Windows Task Manager. When hyperthreading is not enabled, each processor corresponds to a processor core. Affinity masks and processor cores are beyond the scope of this topic. For more information, see the Windows Server and SQL Server documentation.

· Based on performance testing of the OLTP workload for Microsoft Dynamics AX, we recommend that you maintain one tempdb data file per processor. For more information, see the performance benchmark reports on PartnerSource or CustomerSource.

· Isolate tempdb on dedicated storage, if you can. We recommend that you move the primary data file and log file for tempdb to high-speed storage, if high-speed storage is available. The Microsoft Dynamics AX database runs in read committed snapshot isolation (RCSI) mode. In RCSI mode, row versions are stored in tempdb. By creating multiple files for tempdb data, even if these files reside on the same storage device, you can improve the performance of tempdb operations.

· Determine the size of the tempdb data files and log files. You must create one primary data file and one log file. Determine how many additional, secondary data files you require for the tempdb data. For best results, create data files of equal size. The total number of data files must equal the total number of processor cores. The aggregate size of the primary data file and all other data files must equal the total data size that you determined for the tempdb database.

· Resize the primary data file and log file for tempdb. Move the primary data file and log file to dedicated storage, if dedicated storage is available. The primary tempdb data file cannot be moved while the instance of SQL Server is running. To complete the move, you must use an ALTER DATABASE statement and restart the instance of SQL Server. For more information, see ALTER DATABASE.

Note: The data files and transaction log files for tempdb can reside on the same storage device.

· If space is available on the drive where tempdb files are allocated, do not configure the autogrow property for data files and log files as a percentage. Instead, configure the autogrow property as a specific number of megabytes. If you can, configure the data files and log files to grow by 100 to 500 MB, depending on the available space. Monitor the data files, and when they grow, adjust the original allocation to prevent automatic growth later. If the autogrow property is configured in megabytes instead of as a percentage, the allocation of space is more predictable, and the chance of extremely small or large growth increments is reduced.

· Monitor the tempdb data files and log files to make sure that they are all sized correctly, and that all data files are of equal size. Use SQL Server Management Studio or a transact-SQL query to view the database properties. Verify that all the data files are of equal size, and that they have the same size as the value that you originally provided. If one or more files have grown, adjust the initial size of all files.